1. FIELD OF THE INVENTION
The invention relates to a method of making cast-iron ingot moulds for use in casting steel ingots, wherein the ingot mould is cast in a sand mould. The invention also relates to an ingot mould made by the method and to a sand moulding box to be used in the method.
2. DESCRIPTION OF THE PRIOR ART
Steel ingots for steel rolling mills and steel forges are generally made by casting liquid steel into cast-iron ingot moulds. The liquid steel either falls into the ingot mould or is introduced at the lower end and rises up the mould, and the mass of the ingot mould is selected so that a major part of the melting heat of melting of the molten metal is led away into the ingot mould.
In order to manufacture ingots with smooth surfaces, proper condition of the interior surface of the ingot mould is important. As the ingot mould is used repeatedly, its inside surface is gradually attacked or corroded, with the particular danger of fast corrosion at the foot or lower end of the mould. This so-called flushing of the lower end of the ingot mould particularly occurs casting downward as a result of the first contact downward stream of liquid metal with the ingot mould. As the surface of the ingot mould becomes increasingly affected, the mould becomes less and less suitable for casting ingots and after a certain lapse of time it has to be rejected.
Ingot moulds themselves are manufactured by casting them into a partitioned sand mould. A sand moulding box has an interior casing and a bottom which for instance are made in one piece and are coupled to an exterior casing by means of a flange connection. Moulding sand is applied between the interior and exterior casings around a model of an ingot mould. The moulding sand is typically first mixed with a synthetic resin, for example a furane resin, so that proper cohesion of the moulding sand is achieved. During casting a major part of the synthetic resin carbonizes, so that the sand must be cleaned thoroughly before it can be re-used. A large proportion of the cost of manufacturing ingot moulds arises in regeneration of the moulding sand and in the cost of the resin consumed.